2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/11243A short review of the measured spectrum of the Cosmic Microwave Background Radiation (CMBR) and implications. Extensions of the Kompaneets equation and Sunyaev-Zel'dovich effect are given.30 pages, 9 figures from lectures at NATO ASI "The Cosmic Microwave Background" Strasbourg 1996Astrophysicstext